Seej Ballista MK2

An improved version of Zheng3's penny ballistafor SEEJ.
http://www.thingiverse.com/thing:23464
http://zheng3.com/seej/

Improvements:
1. rail now holds knock in ensuring that it travels in a straight line
2. knock is a hair deeper allowing a penny to better rest in it horizontally
3. rail is slightly angled upward to get a slight flight angle

TODO:
improve locking pin design, possible using A modification of http://www.thingiverse.com/thing:45737

improve rail design to make